This invention relates generally to assessing the quality and cost of inspections. More specifically, the present invention is directed to a method, system, and software for factoring costs associated with inspection levels and results for assessing and optimizing the overall cost associated with inspections.
Controlling the number of product defects has become an important part of managing the costs and efficiencies associated with manufacturing and distribution processes. Inspection is often used to measure the variation in products as a method to control the number of escaping defects. Unfortunately, inspection is often an imperfect and sometimes expensive process. Product measurements are often corrupted by noise introduced by the measurement or gaging process. Furthermore, there is a lack of systems for evaluating and managing an inspection process so as to trade off the costs of inspection, re-inspection, scrap/rework of products identified as defective and the often large costs associated with escaping defects.
Previously known methods of analyzing the inspection process do not enable the timely, accurate, and efficient calculation of various tradeoffs between inspection accuracy, product specification or tolerance limits, inspection limits, and/or multistage inspection. These methods do not enable the convenient evaluation of an inspection process where the measurement error is dependent on the size of the permissible variation of the product characteristic being measured.
In particular, the quantitative results of making inspection limits more restrictive than specification limits and/or performing multistage inspections have not been available except through time consuming simulation analysis. Running accurate simulations can be very time consuming during inspection tradeoff optimization determination particularly in ranges where the emphasis is on allowing only a few defects per million to pass through.